Conventionally, in a lithography process for manufacturing electron devices such as semiconductor devices (integrated circuits) and liquid crystal display devices, a projection exposure apparatus that transfers an image of a pattern of a mask or a reticle (hereinafter generally referred to as a ‘reticle’) to each shot area on a photosensitive substrate such as a wafer or a glass plate coated with resist (photosensitive agent) (hereinafter referred to as a ‘substrate’ or ‘wafer’) via a projection optical system is used. As this type of projection exposure apparatus, conventionally a reduction projection exposure apparatus by a step-and-repeat method (the so-called stepper) has been mainly used, however, recently, a projection exposure apparatus by a step-and-scan method (the so-called scanning stepper) that performs exposure while synchronously scanning a reticle and a wafer is gathering attention.
In such a projection exposure apparatus, it is required to transfer a finer pattern with a high resolution to cope with higher integration of semiconductor devices and the like. As a method to achieve this aim, the so-called super-resolution technology such as annular (ring-shaped) illumination, bipolar illumination and quadrupole illumination, and the like, which improve the resolution by setting an incident angle of illumination light to a reticle to a predetermined angle, has come into practical use.
Further, an attempt to improve the resolution and a depth of focus by optimizing a polarization state of illumination light in accordance with an array direction of patterns on a reticle has been also proposed. This method is a method in which contrast of a transferred image and the like are improved by making a polarization direction of a linearly polarized illumination light be a direction orthogonal to a periodic direction of the patterns (a direction parallel to a longitudinal direction of the pattern) (e.g. Non-patent Document 1).
Also, as another method, in annular illumination, an attempt to improve the resolution, contrast of a projected image and the like by making a polarization direction of illumination light in an area where the illumination light is distributed within a pupil plane of an illumination optical system coincide with a circumferential direction of a circle having an optical axis as its center has been made (e.g. refer to Patent Document 1).
In this manner, in the case the resolution and contrast of a projected image and the like are improved by optimizing a polarization state of illumination light, it is preferable to confirm the polarization state of the illumination light. In this case, a method for measuring the polarization state of the illumination light on a plane conjugate with a pupil plane of an illumination optical system can be considered. However, in this method, various optical properties of the illumination optical system and a projection optical system such as a size, a shape and a position of illumination need to be measured, and therefore a proposal of a comprehensive measurement method is expected.
Further, in the case a polarization direction of illumination light is set so as to be different at different positions within the pupil plane of the illumination optical system, the propagating velocity of the illumination light is different depending on the polarization direction due to anisotropic nature of an optical element constituting a part of the projection optical system, and the like. Accordingly, even when the illumination light passes through the same projection optical system, a wavefront of the illumination light via the projection optical system is different depending on the polarization direction of the illumination light. Thus, since some of various optical properties of the illumination optical system and the projection optical system are not completely independent, a measurement method of optical properties in which these dependencies are taken into consideration is expected be offered.
Non-patent Document: Thimothy A. Brunner, et al.: “High NA Lithographic imaging at Brewster's angle”, SPIE (USA) Vol. 4691, pp. 1-24 (2002)
Patent Document Kokai (Japanese Unexamined Patent Application Publication) No. 6-053120